Vitamin D deficiency is associated with a substantially increased risk of dementia and Alzheimer’s disease in older people, according to the most robust study of its kind ever conducted. An international team, led by Dr David Llewellyn at the University of Exeter Medical School, found that study participants who were severely Vitamin D deficient were more than twice as likely to develop dementia and Alzheimer’s disease. The team studied elderly Americans who took part in the Cardiovascular Health Study. They discovered that adults in the study who were moderately deficient in vitamin D had a 53 per cent increased risk of developing dementia of any kind, and the risk increased to 125 per cent in those who were severely deficient.